I'd just like to point out that a personal attack is only argumentum ad hominem when it is used as the premise of an argument. e.g. "You are an idiot, therefore you are wrong" is an ad hominem argument, but "You are wrong, therefore you are an idiot" is not an ad hominem argument (though it is still abusive). This is one of those things that just irritates me when people get it wrong.

I agree on all other points though.